On Thu, 27 Mar 2008, Christos Hatzis wrote: > Yes, indeed. The help page says that @ extracts the contents of a slot in > S4 objects. But you mention below that this 'works' for S3 objects because > S4 slots are stored as attributes. Doesn't this mean that @ is currently > implemented to access attributes of objects in general (attributes of S3 > objects or slots of S4 objects that are implemented as attributes)? I > realize that this might change in the future...
Yes, but it will change, quite possibly for 2.7.0. > > -Christos > >> -----Original Message----- >> From: [EMAIL PROTECTED] >> [mailto:[EMAIL PROTECTED] On Behalf Of Prof Brian Ripley >> Sent: Thursday, March 27, 2008 3:17 AM >> To: Christos Hatzis >> Cc: r-help@r-project.org >> Subject: Re: [R] Rule for accessing attributes? >> >> Oh please don't recommend misuse of @ to those already confused. >> >> @ is for accessing slots in S4 objects. This 'works' because >> they happen to be stored as attributes. See the help page >> (and the warning that it does no checking - we may change that). >> >> Similarly, >> >> plt$title <- "My Title" >> >> works because the package maintainer (of ggplot2, >> unmentioned?) has chosen to set things up that way. R is >> very flexible, and there is plenty of scope for package >> authors to do confusing things. >> >> On Thu, 27 Mar 2008, Christos Hatzis wrote: >> >>> You need to use the '@' operator to directly access attributes (not >>> elements) of objects: >>> >>>> [EMAIL PROTECTED] >>> [1] "x" "y" "z" >>> >>> See ?'@' for more details. >>> >>> -Christos >>> >>>> -----Original Message----- >>>> From: [EMAIL PROTECTED] >>>> [mailto:[EMAIL PROTECTED] On Behalf Of Tribo Laboy >>>> Sent: Thursday, March 27, 2008 12:16 AM >>>> To: r-help@r-project.org >>>> Subject: [R] Rule for accessing attributes? >>>> >>>> Hi ! >>>> >>>> I am a new user and quite confused by R-indexing. >>>> >>>> Make a list and get the attributes >>>> lst <- list(x = 1:3, y = 4:6, z = 7:9) >>>> attributes(lst) >>>> >>>> This returns: >>>> >>>> $names >>>> [1] "x" "y" "z" >>>> >>>> I can easily do: >>>> >>>> nm <-names(lst) >>>> >>>> or >>>> >>>> nm <-attr(lst,"names") >>>> >>>> which both return the assigned names of the named list >> 'lst', but why >>>> then this doesn't work: >>>> >>>> lst$names >>>> >>>> ? >>>> >>>> I am confused ... Moreover, I noticed that some of the >> objects (e.g. >>>> plot objects returned by ggplot) also have attributes when >> queried by >>>> the 'attributes' function, but they are accessible by the >> $ notation. >>>> (e.g. >>>> >>>> xydf <- data.frame(x = 1:5, y = 11:15) plt <- ggplot(data = xydf, >>>> aes(x = x,y = y)) + geom_point() >>>> attributes(plt) >>>> >>>> Now we can change the title: >>>> >>>> plt$title <- "My Title" >>>> plt >>>> >>>> So is it some inconsistency or am I missing something important? >>>> >>>> ______________________________________________ >>>> R-help@r-project.org mailing list >>>> https://stat.ethz.ch/mailman/listinfo/r-help >>>> PLEASE do read the posting guide >>>> http://www.R-project.org/posting-guide.html >>>> and provide commented, minimal, self-contained, reproducible code. >>>> >>>> >>> >>> ______________________________________________ >>> R-help@r-project.org mailing list >>> https://stat.ethz.ch/mailman/listinfo/r-help >>> PLEASE do read the posting guide >>> http://www.R-project.org/posting-guide.html >>> and provide commented, minimal, self-contained, reproducible code. >>> >> >> -- >> Brian D. Ripley, [EMAIL PROTECTED] >> Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ >> University of Oxford, Tel: +44 1865 272861 (self) >> 1 South Parks Road, +44 1865 272866 (PA) >> Oxford OX1 3TG, UK Fax: +44 1865 272595 >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> >> > > -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
